Amzad,

As Bill pointed out, a TIC/TOC analyzer is a good way to go, but if 
you don't have access to a TIC/TOC, you might want to look at the 
Gandhi et al. (2004) paper as an alternative technique.

Gandhi H., Wiegner T.N., Ostrom P.H., Kaplan L.A. and Ostrom N.E. (2004)
Isotopic (13C) analysis of dissolved organic carbon in stream water 
using an elemental analyzer coupled to a stable isotope ratio mass 
spectrometer.
Rapid Communications in Mass Spectrometry, 18: 903-906

Good luck!

Cheers,
Simon



>Amzad
>We use a TIC/TOC analyzer system interfaced to a continuous flow IRMS for
>13C analysis of DIC and DOC. In this system, phosphoric acid drives DIC to
>CO2, which is purged from the sample. Then a persulfate digestion is used to
>convert DOC to DIC, which is converted to CO2 and transferred to He carrier.
>-Bill
>
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>Bill Holmes
>UC-Davis Stable Isotope Facility
>2220 Plant & Env Sci
>One Shields Ave
>Davis, CA 95616
>Phone: (530) 752-8100
>FAX: (530) 752-4361
>stableisotopefacility.ucdavis.edu
>~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
>
>
>
>-----Original Message-----
>From: Stable Isotope Geochemistry [mailto:[log in to unmask]] On Behalf
>Of Amzad Hussain
>Sent: Monday, April 07, 2008 12:04 PM
>To: [log in to unmask]
>Subject: [ISOGEOCHEM] stable isotopic measurement of DOC
>
>Hi everyone
>I would like to know how CO2 can be extracted from Dissolved Organic
>Carbon for stable isotopic analysis?
>
>Thanks
>Amzad


-- 
*****
Simon Poulson
Research Associate Professor
Dept. of Geological Sciences & Engineering MS-172
University of Nevada - Reno
1664 N. Virginia St.
Reno, NV 89557-0138. USA
(775) 784-1104
Fax: (775) 784-1833
[log in to unmask]
http://www.mines.unr.edu/isotope/simonhome.html
*****